Electron gun and socket structure



O 9 6 A. C.'GRIMM ETAL 3,277,326

ELECTRON GUN AND SOCKET STRUCTURE Filed June 20, 1963 INVENTORS ALBERT c. GR/MM BY FRED GHAMMERSAND ATTORNEY United States Patent O ice ELECTRON GUN AND SOCKET STRUCTURE Albert C. Grimm, Lancaster, and Fred G. Hammersand,

East Petersburg, Pan, assignors, by mesne assignments,

to the United States of America as represented by the United States Atomic Energy Commission Filed June 20, 1963, Ser. No. 289,454 Claims. (Cl. 313-40) The invention disclosed herein was made under, or in, the course of Contract No. AT(04-3)363 with the United States Atomic Energy Commission.

The present invention relates generally to electron guns, and in particular to an improved electron gun and socket structure for high power, microwave tubes such as, for example, klystron tubes. The structure is particularly designed to allow easy dismantling of the electron gun 'for ready access to, and replacement of, components therein, such as the cathode button, while providing an improved means for socketing the tube in applications where the socket is located under oil.

Electron guns for klystron tubes, traveling wave tubes, and the like, are usually constructed of an assemblage of machined or stamped parts welded together in proper relationship to one another. Such construction is of a permanent nature and does not lend itself to the rebuilding of the electron gun, should the gun become inoperable. The present invention therefore, overcomes the abovenoted shortcomings by providing an improved mechanical structure for an electron gun and socket structure which can be readily rebuilt without in any way sacrificing the electrical performance of the device, while additional- 1y providing a readily demountable, low inductance electrical connection which is easily aligned and socketed.

Accordingly, it is an object of the present invention to provide an improved electron gun and socket structure adapted to allow ready disassembly of parts.

It is another object of the present invention to provide an improved electron gun structure whereby the cathode button may be replaced in the electron gun without cutting or welding.

It is still another object of the present invention to provide an electron gun structure wherein the electrode shape and spacings between electrodes is inherently controlled upon assembly of the gun.

It is yet another object of the present invention to provide an electron gun and socket structure for use with a klystron tube which is socketed under oil, wherein the heater terminal is exposed to view in the klystron oil tank, whereby the klystron may readily be aligned and mounted to the socket.

It is still another object of the present invention to provide an improved electron gun and stocket structure having a readily demountable, low inductance contact for passing high cathode current pulses, while minimizing the amount of capacity added to the cathode-anode capacity.

Still another object of the present invention is to provide an improved electron gun structure including a heat shield assembly of improved heat shielding characteristics.

Yet another object of the present invention is to provide a flexible socketing arrangement which compensates for misalignment of mating components therein.

Additional objects and advantages of the invention will become apparent from the following description and claims considered together with the accompanying drawing, of which FIGURE 1 is a simplified cross-sectional view showing the improved electron gun and socket structure of the present invention used in conjunction with a klystron tube, wherein the tube is shown partially demounted from the socket.

3,277,326 Patented Oct. 4, 1966 FIGURE 2 is a reduced bottom view of the cathodefocus electrode assembly.

FIGURE 3 is a enlarged cross-sectional view taken along line 33 of FIGURE 2.

FIGURE 4 is a reduced top view of the cathode-focus electrode support assembly showing the heater coil in place. FIGURE 5 is an enlarged cross-sectional view taken along line 5--5 of FIGURE 4.

FIGURE 6 is a reduced top view of the socket shown in FIGURE 1.

As previously noted, the improved construction of the electron gun and socket structure of the present invention provides a readily demountable, low inductance mechanical design, and exhibits precisely reproducible electrical characteristics, mechanical stability under shock and/ or vibration, high thermal efliciency, and simplicity of construction and subsequent repair. To these ends, the im proved structure, as shown in FIGURE 1, preferably in cludes an outer housing-insulator assembly 12 which is rigidly secured to the bottom end of a klystron tube 14 (depicted in phantom line). A cathode-focus electrode support assembly 16 is coaxially secured within the housing-insulator assembly 12. A cathode-focus electrode assembly 18 is demountably secured in coaxial relation to an end of the cathode-focuselectrode support assembly 16. A heater post assembly 20 is coaxially secured in insulated relation within the same end of the cathode-focus electrode support assembly 16, and in turn coaxially supports a heat shield assembly 22. A heater coil assembly 24 is sandwiched between the cathode-focus electrode assembly 18 andthe heat shield assembly .22, the combination of assemblies 18, 22, 24 thus providing the means for efiiciently heating the cathode to supply electrons for the beam. A readily demountable, low inductance, electrical connection is provided to the smooth inside surface of the cathode-focus electrode support assembly 16 by means of a coaxial, double-contact socket assembly 26. The inner contact of the socket assembly 26 provides a quick connection for introducing current to the heater coil assembly 24, and the outer contact thereof provide a quick connection for both introducing the high cathode pulsed current to the gun and current to the heater coil assembly 24. A horizontally movable, captive bearing, base assembly 28 provides a mounting base for the socket assembly 26 while compensating for major misalignment between the electron gun and socket structure.

Referring now in greater detail to FIGURE 1 there is shown the improved electron gun and socket structure adapted for utilization with a klystron tube 14. Although the invention is herein particularly described in conjunction with a klystron tube, it is to be understood that the invention may in general be incorporated in vacuum tubes, traveling wave tubes, etc. of related construction. The improved electron gun is mounted securely to the bottom of the associated klystron tube 14 by means of a gun support ring 30, which is in turn permanently brazed to the anode of the klystron tube 14. A thin copper-nickel gun Welding flange 32 is concentrically brazed to the outer circumference of the gun support ring 30, forming thus a means for securing and sealing the improved electron gun structure to the klystron tube.

More particularly, considering the construction of the outer, housing-insulator assembly 12, a gun locating ring 34 is concentrically sealed to one end of an elongated heavy stainless steel housing 36 the other end of which flares radially inward to define at such end a generally smaller cross section. A thin, copper-nickel welding ring 38 is sealed in coextending relation to the stainless steel housing 36 in perpendicular relation to the gun locating ring 34. The adjacent edges of the welding ring 38 and the welding flange 32 are vacuum-sealed together in rigid relation by suitably brazing or welding the edges together along their entire circumference. A stress-relief sealing ring 40 is concentrically brazed along one edge thereof to the outside curvature of the inwardly flared end of the housing 36. The opposite edge of the stress-relief sealing ring 40 is concentrically brazed to the large end of a teacup shaped hollow insulator 42; the wall of the insulator 42 extends in tapering configuration away from the stressrelief ring 40 to define the tea-cup shape. The opposite, smaller end of the tea-cup insulator 42 has concentrically brazed thereto a thin, flanged ring 44.which extends coaxially a short distance therefrom. As may be seen from the figure, the inwardly flared end of housing 36 extends beyond, and protrudes within, the adjacent end of hollow insulator 42 a short distance, to equalize the electrical stress on the insulator 42.

Considering now in greater detail the cathode-focus electrode support assembly 16, a stainless steel support tube 46 of suitable diameter is machined a substantial distance along the outer circumferential surface of the upper end thereof to define an upper shoulder 48 thereabout. The small end of support member 50 is concentrically fitted over the machined end of the tube 46 to bear against the upper shoulder 48. The wall of support member 50 flares radially outward from the end which bears against the upper shoulder 48, to define an end having a relatively larger diameter. A cathode-focus electrode assembly support ring 52 is machined about its outer circumference at the bottom of the part to define a shoulder thereabout. The shoulder of ring 52 mates with the edge of the larger daimeter end of the member 50 to provide means for concentrically positioning and securing the ring 52 thereto. The various shoulders formed in the tube 46, support member 50, and support ring 52, thus provide means for self-jigging the cathode-focus electrode support assembly 16, whereupon the individual elements may be brazed together. After the parts comprising the cathode-focus support assembly 16 have been brazed together the assembly is placed on an internal mandrel and a substantial distance along the outer circumferential surface at the lower end of support tube 46 and the upper step 49 on the support ring 52 are machined concentric. The machined cathodefocus electrode support assembly is slipped into flanged ring 44 and by means of a jig, the upper shoulder 49 of the support ring 52 is both positioned axially and held concentric to the small diameter of the gun locating ring 34 so that when the support tube 46 is welded along its entire circumference to the flared ring 44, the upper shoulder 49 of support ring 52 will be accurately positioned and concentric to the smaller diameter of the gun locating ring 34.

Considering now the cathode-focus electrode assembly 18 in more detail, a hydroformed focus electrode 54 having a generally U shaped cross-section, has concentrically brazed therein a focus electrode mounting ring 56 (see FIGURES 1, 2, and 3). The mounting ring 56 has a plurality of arcuate slots 58 cut therein in equally spaced relation along the circumferential length thereof. A concave, circular button cathode 60 is concentrically mounted to the mounting ring 56 by means of a suitable plurality of evenly spaced, cathode support wires 63, which extend at one end radially into the circumferential edge of the cathode 60. The free ends of wires 62 are demountably fixed to mounting ring 56 by means of threaded screws 64; the wires are suitably secured to the screws 64, as for example, by inserting the wires into axial holes bored in the screws and brazing them together. If desired, the ends of the wires 62 may be rigidly secured to the mounting ring 6 simply by extending the ends through a spaced series of holes bored through the mounting ring 56, and brazing the ends directly to the ring. The cathode 60 is arranged so that the concave surface thereof faces towards the focus-electrode 54 and the klystron tube 14. Facing in this direction the cathode 60 is jigged to both hold it concentric with and locate its axial position relative to the lower surface of the focus electrode 54 whereupon the free ends of wires 62 and 63 are welded together.

As seen in FIGURE 1, the end of tube 46, opposite the end welded to the thin, flanged ring 44, extends beyond the upper shoulder 48 formed therein and towards the facing, convex surface of the button cathode 60. The heater post assembly 20 of previous mention is concentrically mounted within the extended end of the tube 46. Considering more particularly the heater post assembly 20, a current conducting post 70 is brazed to a washer 72 which is, in turn, coaxially secured to an insulating washer 74 of generally larger diameter. The insulating washer 74 is concentrically aflixed, as by brazing, to a post support flange 76. The outer periphery of the post support flange 76 extends coaxially along, and snugly within, the support tube 46 to terminate evenly with the end of the tube. The adjacent edges of the tube 46 and the post support flange 76 are welded together along the entire circumference thereof. Upon proper assembly of the heater post assembly 20, the post 70 extends from the end of the tube 46 in coaxial and insulated relation therewith. The upper end of the current conducting post 70 which extends towards cathode 60, is drilled and tapped to provide an axially threaded bore therein.

The heat shield assembly 22 is formed by riveting four molybdenum concave heat shields 78 and one stainless steel concave heat shield 80 together in evenly spacedapart relation, the riveting being effected with a suitable plurality of spaced, double-ended nickel rivets 82. The concave surfaces of the shields are disposed to face towards the klystron tube 14, to match the orientation of the cathode 60. The heat shield assembly 22 has a large axial hole 84 formed through the center of each of the shields 78, and a small axial hole through heat shield 80. The stainless steel heat shield 80 has a formed eyelet 86 coaxially welded to the axial hole formed in the center thereof. The heat shield assembly 22 is concentrically located to the end of the post 70 by means of eyelet 86 and is held in position by means of a screw 88, the head of which will pass through the holes 84 in heat shields 78, but not the hole in shield 80, screwed into the threaded bore within the post 70.

Considering the heater coil assembly 24, the molybdenum heat shield 78 nearest the button cathode 60 is spaced a distance therefrom to allow a heater coil 90 of suitable configuration to be sandwiched therebetween. Tabs 79 lanced into heat shield 78 confine the heater coil 90 in position. The heater coil 90 is coated with ceramic insulation and has two heavy nickel tabs 92 and 94 welded at either end thereof. Tab 92 is demountably secured by means of screws to a suitable pillar block 96 secured to the outer circumference of the heat shield 78 nearest the cathode 60. The heavy nickel tab 94 is demountably secured as by means of screws to the cathodefocus electrode assembly support ring 52.

As may be seen by referring to FIGURES 1, 4, and 5, the mounting ring 56, focus electrode 54 and attached button cathode 60 are positioned in concentric relation to the cathode-focus electrode assembly support ring 52 by means of steps 57 and 49 and are demountably secured to the cathode-focus electrode assembly support ring 52 by means of a suitable plurality of leaf-springs 98. The springs 98 are mounted to the support ring 52 and spaced therefrom by suitable blocks 100 and fastening screws 12. The cathode-focus electrode assembly 18 may thus be re moved simply by twisting the assembly 18 so that the springs 98 are disengaged from their position on the edge of the arcuate slots 58 of the focus electrode mounting ring 56, whereupon withdrawal of the assembly 18 is possible. The leaf-springs 98 could be replaced by suitable coil springs mounted to the support ring 52 and adapted to provide a spring-loaded clamping action against the achieved upon assembly of the device.

mounting ring 56 to secure same thereto in demountable relation.

Consider now in greater detail the coaxial, double-contact socket assembly 26 and base assembly 28. The socket assembly 26 is mounted upon the base assembly 28 of previous mention which is formed more particularly of plates 104 and 106 between which is confined a plurality of captive ball-bearings 108. Three setscrews 110 are provided to secure the plate 104 to the plate 106 and permit movement of plate 104 relative to plate 106 so that the tube will be properly aligned and socketed upon the assembly 26.

Regarding now the socket assembly 26 of previous mention, a socket support tube 116 is rigidly secured at one end to the plate 104 as by brazing, to extend therefrom a substantial distance. The socket support tube 112 is circumferentially bisected to define an upper and lower socket support tubes 114 and 116 respectively. A short length of bellows 118 is secured at either end thereof as by brazing to the adjacent ends of socket support tubes 114 and 116. An annularly shaped corona shield 120 is circumferentially disposed circumjacent about the bellows 118 and is secured to the outer circumference of the adjacent end of tube 114. An insulator 122 is rigidly secured within the upper tube 114 at approximately the midpoint thereof. An electrically conductive spring support 124 is suitably secured to the insulator 122 by means of a setscrew 126, which screw also acts as a connector terminal for an incoming heater lead 128. The lead 128 is herein introduced through an opening in the corona shield 120 and a hole in the lower tube 116, although it may be introduced in any other convenient manner. The extended end of spring support 124 is machined to receive, in snugly secured relation, one end of a heavy spring 130. Spring 130 extends upwardly therefrom a substantial distance to secure snugly one end of heater connector 132. Heater connector 132 fits circumjacent about the heater post 70 of the electron gun structure when the klystron tube is socket-ed, i.e., mounted upon the socket assembly 26.

A 'hollowguide post 136 is concentrically disposed circumjacent about the heater connector 132, spring 130, and spring support 124, and is held in place by securing the lower end thereof to the upper support tube 114. Note that the extended end of guide post 136 extends slightly beyond the end of connector 132, and further tapers radially inward to act as a socket aligning guide. A series of circumferentially spaced, axially extending resilient finger contacts 138 are secured in electrically conducting relation at their upper ends to the tube 114 and extend axially downward therefrom to provide a cylindrical, low inductance contact for the high, tube pulsed currents and path for the heater current. At such time as the klystron tube 14 and electron gun are socketed upon the socket assembly 26, the resilient finger contacts 138 press outwardly against the smooth inner surface of the stainless steel tube 46 of the electron gun, thereby providing a large contact area, and a low inductance current path, from the stainless steel support tube 46 to the upper socket support tube 114.

Accurate control of the electrodeshape' and spacings between electrodes in the electron gun of FIGURE 1 is essential if uniform electrical characteristics are to be achieved. The construction of the present invention is such that accurate control of the spacings can be simply Further the design is such that the various parts of the gun can be removed and replaced in case of failure of any part. This feature is accomplished without introducing any holes, screws, or protuberances into the region of high electric field that could cause regions of high electrical stress and arcing.

The electron gun is accurately positioned at the bottom of the klystron 14 by means of the flange 30 and ring 34. A vacuum seal is made by welding or brazing the edges of the thin, flexible, copper-nickel welding flange 32 and ring 38. To remove a defective electron gun the weld head on the flange 32 and ring 38 edge is cut with suitable scissors. A new gun is then easily slipped in place and the flange and new associated ring are rewelded together.

Socketing of a high-voltage electron gun, such as herein disclosed, which operates under oil is facilitated by placing the terminal for the heater inside the electron gun near the top of the insulator 42. With such a construction it is then possible to place the heater connector 132 of the socket close to the surface of the oil as heretofore set forth in the description of the socket assembly 26.

Regarding the heat shield assembly 22, excessive dissipation of radiant energy which possibly could leave the heater coil 90 from the side opposite the cathode 50 is reduced to a minimum by the nest of a plurality of molybdenum heat shields 78 and one stainless steel shield 80 riveted together with small nickel rivets 82. To reduce the thermal conduction loss to a minimum the rivets 82 are made of poor thermal conducting material and the nest of shields is supported by a single eyelet 86 from the heater terminal post 70. To further conserve thermal conduction losses, one leg of the heater coil 90 is connected directly to the shield assembly 22, which is formed generally of an electrically conductive material. Thus the heat shield assembly 22 serves as one side of the electrical connection for the heater coil 90 and the heat lost by conduction from this leg of the heater coil 00 is minimized.

The guide post 136 serves to guide the flexible finger contacts 138 and the heater connector 132 into mating position with the stainless steel tube 46 (cathode termi nal), and current conducting post 70 (heater terminal) respectively of the electron gun. Additionally, guide post 136 protects the heater connector 132 from damage while supporting the cathode contacts 138 and corona shield Compensation for vertical or horizontal misalignment and tilt between the klystron tube 14 and socket assembly 26 is provided by the system of captive ball bearings 108 between plates 104 and 106 and the flexible bellows 118 placed between socket support tubes 114 and 116.

Misalignment between the heater connection 132 and current conducting post 70 is compensated for by the stiff spring 130, while engagement of the connector 132 to the post 70 is facilitated by tapering both the ends thereof. A low inductance electrical connection is made to the inside surface of the tube 46 due to the large area of contact of the cylindrical ring of resilient finger contacts 138. The finger contacts 138 are located at the base of the guide post 136 so that no mechanical stress is applied at the cathode end of the stainless steel support tube 46. Furthermore, radial distortion of the tube 46 is prevented since the contact region thereof is radially supported thereabout by the flanged ring 44. As shown in the drawing, the finger contacts 138 point downwardly towards the base assembly 28 and the ends of the contacts are suitably tapered to prevent the possibility of deforming them. Furthermore the radial support provided by the upper tube 114 disposed circumferentially within the contacts 138 limits the amount of deformation the contacts make inwardly and prevent same from flexing beyond the yield point of the metal.

Since the major portion of the socket assembly 26 is circumjacent within the cylindrical tube 46 of the electron gun, the socket assembly 26 adds little capacitance between the cathode 60 and anode of the electron gun and tube. The major portion of the socket assembly 26 which contributes slightly to the added capacitance is the corona shield 120. This shield could be made an integral part of the electron gun and thus would introduce relatively little additional capacitance between cathode and anode. Alternately, for example, the corona shield could be supported by an annular member rigidly secured in coaxial relation to the upper tube 114 and divorced from contact with the bellows 118. Flexibility in an axial direction could be supplied to the corona shield by mounting an outer annular portion thereof (which will bear against the insulator 42 upon socketing of the klystron tube) on springs placed therebetween and reciprocally securing the two elements together by means of retaining screws passing through the center of the springs.

While the invention has been disclosed with respect to a single preferred embodiment, it will be apparent to those skilled in the art that numerous variations and modifications may be made Within the spirit and scope of the invention, and thus it is not intended to limit the invention except as defined in the following claims.

What is claimed is:

1. An improved electron gun and socket structure for high-power microwave tubes comprising (a) housing assembly means having an electrically conductive upper axial portion and an electrically nonconductive lower axial portion coaxially sealed coextensive thereto, said housing assembly means having a central axis;

(b) hollow tubular support means concentrically disposed along the axis of said housing assembly means, one end thereof being secured in sealed relation to said nonconductive axial portion, the other end thereof extending into said conductive axial portion;

(c) an annular cathode-focus electrode assembly including a circular cathode demountably secured in coaxial relation circumjacent about the extended end of said tubular support means;

(d) a heater post assembly rigidly secured in coaxial electrically insulated relation within said tubular support means;

(e) coil means disposed in adjacent spacial relation to said cathode to heat same when energized with electric current;

(f) heat shield means disposed in adjacent spacial relation against said coil means on the side thereof opposite said cathode, said heat shield means being demountably secured to said heater post assembly; and

(g) demountable socket means including a hollow guide post and a first contact disposed in coaxial relation to a second contact means and electrically insulated therefrom, said guide post adapted to coaxially engage and fit within said hollow tubular support means, said first contact means disposed generally within said hollow guide post and adapted to provide an electrical connection with said heater post assembly, said second contact means disposed generally about said hollow guide post and adapted to provide an electrical connection with said tubular support means, and terminal input means integral with said first and said second contact means for introducing electrical currents thereto.

2. The improved electron gun and socket structure according to claim 1 wherein (a) said annular cathode-focus electrode assembly further comprises an annular focus electrode of generally U-shaped cross section, a flat mounting ring concentrically secured within the annular U of said focus electrode, said fiat mounting ring having a plurality of arcuate slots formed therein along the length thereof;

(b) said hollow tubular support means further comprises an annular support ring coaxially secured to the extended end thereof, clamping means including a spring secured to said annular support ring and spaced along the length thereof, said clamping means adapted to pass through said arcuate slots and engage said flat mounting ring to secure in demounta-ble relation said mounting ring to said support ring upon assembly thereof.

3. The improved electron gun and socket structure according to claim 1 wherein said heat shield means comprises (a) a plurality of thin circular shields coaxially sandwiched in evenly spaced-apart relation, a plurality of rivets formed of poor thermal conducting material and disposed to support said shields in said spaced'apart relation, wherein the thin circullar shield furthermost from said cathode is formed of stainless steel, and means for demountably securing in electrically conductive relation said stainless steel shield to said heater p-ost assembly.

4. The improved electron gun and socket structure according to claim 1 wherein said demountable socket means further comprises (a) a cylindrical socket support coaxially secured at one end to said hollow guide post;

(b) a flexible bellows coaxially secured in coextensive relation within the length of said cylindrical socket support;

(c) horizontally slidable base means rigidly secured to the end of said cylindrical socket support opposite that end secured to said guide post;

((1) said first contact means being coaxially secured in electrically insutlated relation within said cylindrical socket support and extending therefrom into said hollow guide post;

(e) said second contact means comprising a cylindrical contact disposed cir-cumjacently about said cylindrical socket support in electrically conducting relation therewith.

5. The apparatus according to claim 4 wherein (a) said first contact means further comprises -a resilient spring coaxially secured in electrically insulated relation within said cylindrical socket support, and a hollow connector coaxially secured to said resilient spring and adapted to mate with said heater post assembly; and

(b) said cylindrical contact of said second contact means further comprises a plurality of contiguous resilient finger contacts disposed in axially extending relation circumjacent about said cylindrical socket support in electrically conductive relation therewith.

References Cited by the Examiner UNITED STATES PATENTS 1/1949 Potter 313-49 X 6/1954 Veronda 31345 X 

1. AN IMPROVED ELECTRON GUN AND SOCKET STRUCTURE FOR HIGH-POWER MICROWAVE TUBES COMPRISING (A) HOUSING ASSEMBLY MEANS HAVING AN ELECTRICALLY CONDUCTIVE UPPER AXIAL PORTION AND AN ELECTRICALLY NON-CONDUCTIVE LOWER AXIAL PORTION COAXIALLY SEALED COEXTENSIVE THERETO, SAID HOUSING ASSEMBLY MEANS HAVING A CENTRAL AXIS; (B) HOLLOW TUBULAR SUPPORT MEANS CONCENTRICALLY DISPOSED ALONG THE AXIS OF SAID HOUSING ASSEMBLY MEANS, ONE END THEREOF BEING SECURED IN SEALED RELATION TO SAID NONCONDUCTIVE AXIAL PORTION, THE OTHER END THEREOF EXTENDING INTO SAID CONDUCTIVE AXIAL PORTION; (C) AN ANNULAR CATHODE-FOCUS ELECTRODE ASSEMBLY INCLUDING A CIRCULAR CATHODE DEMOUNTABLY SECURED IN COAXIAL RELATION CIRCUMJACENT ABOUT THE EXTENDED END OF SAID TUBULAR SUPPORT MEANS; (D) A HEATER POST ASSEMBLY RIGIDLY SECURED IN COAXIAL ELECTRICALLY INSULATED RELATION WITHIN SAID TUBULAR SUPPORT MEANS; (E) COIL MEANS DISPOSED IN ADJACENT SPACIAL RELATION TO SAID CATHODE TO HEAT SAME WHEN ENERGIZED WITH ELECTRIC CURRENT; 